The present invention relates to a method for producing planar surfaces having very fine peaks in the micron range or smaller, for example, planar field emission cathodes, of conductive or semiconductive material, by filling cavities in matrices of dielectric material and, if desired, subsequently removing the matrix containing the cavities.
The method under discussion here relates to the manufacture of the very finest metal, i.e. conductive, needles of a given length and orientation in a large number of dielectric materials. It is possible in this connection for the metal needles to either remain in the dielectric material, e.g. when they are used for embedded dipole antennas for the infrared wave art, or to be exposed, for example, for use in field emission peaks or large-area field emission cathodes. For this case, a metallic base is required to hold a plurality of metallic peaks in the form of a bed of needles.
In the prior art, individual, freestanding field emission peaks have been produced by electrolytically sharpening the point of a fine wire, usually a tungsten wire. The field emission peak is introduced into a high vacuum. If the tensile stresses are relatively low, very high and simultaneously very well bundled electron beams can be obtained from such field emission peaks to be used, for example, in grid electron microscopy. In the prior art, large area arrangements of many field emission peaks have been produced according to methods customary in the semiconductor art, i.e. covering with a mask, subsequent wet chemical etching or ion etching, as well as oblique vapor-deposition. However, this prior art method is able to furnish a uniform arrangement of field emission peaks over a total area of only a few cm.sup.2 with a density of up to about 10.sup.5 /cm.sup.2.
Such methods for producing field emission surfaces are very costly. Several process parameters must be optimized and the process includes a series of different, complicated process steps.